Hydroxyethyl piperazine compounds are generally made by reacting an excess of ethylene oxide with piperazine. One of the difficulties is that, in addition to producing mono-hydroxyethyl piperazine, the ethoxylation of piperazine leads to the formation of di-hydroxyethyl piperazine as a byproduct along with any unreacted ethylene oxide and/or piperazine. Whether a batch or a continuous process is employed, the resulting reaction mixture must be separated by multistep distillation to isolate the desired hydroxyethyl piperazine compound from the by-products, for example see U.S. Pat. No. 6,013,801.
Reactive distillation is well known, for example see, U.S. Pat. No. 5,368,691, and is generally favored for the case of reacting away an azeotrope and driving a reaction to completion. For example see U.S. Pat. No. 4,435,595 for the production of methyl acetate, US Patent Application No. 2013/0197266 for the production of ethyl acetate, US Patent Application No. 2013/0310598 for the production of glycolate ester oligomers, US Patent Application No. 2014/03787712 for the alkanolysis of polyether polyols to polyester polyols, and US Patent Application No. 2014/0364655 for producing allyl alcohols.
It would be desirable to have a process to make hydroxyethyl piperazine compounds which favors the production of mono-hydroxyethyl piperazine and/or eliminates the need for a separate multistep distillation.